How to change the angle of an edge in a cylinder
The add-on LoopTools can change a non-circular loop to a circular loop.  Add ons need to be installed.  33 second task.  Search info here at BSE.




Example. LoopTools changes a beformed cylinder into a more regular frustrum. We need only to select in Edit Mode the Top and Bottom loops. Regular Cylinder is easy variation.


You need to be able to specify one or more starting points in your mesh so the equal angle bend can begin.  This a design goal for you to state, not a difficult technical issue.  This is not quite so obvious in your image since the shape is a cylinder rather than a more common case of a plane.  





Armature with constraints can specify an angle, and circular arc.
A subdivided curve with a Curve Constraint may be useful.
Proportional Edit may be useful
If you want manual labor, you change change the pivot center for rotation scaling to be the cursor and move the cursor to the current selection.